How to use the vega-scale.interpolate function in vega-scale

} else {
        error(`Scale type ${type} does not support interpolating color schemes.`);
      }
    }
  }

  // given a range array for an interpolating scale, convert to interpolator
  if (range && isInterpolating(type)) {
    return scale.interpolator(
      interpolateColors(flip(range, _.reverse), _.interpolate, _.interpolateGamma)
    );
  }

  // configure rounding / interpolation
  if (range && _.interpolate && scale.interpolate) {
    scale.interpolate(getInterpolate(_.interpolate, _.interpolateGamma));
  } else if (isFunction(scale.round)) {
    scale.round(round);
  } else if (isFunction(scale.rangeRound)) {
    scale.interpolate(round ? interpolateRound : interpolate);
  }

  if (range) scale.range(flip(range, _.reverse));
}